The Big I project contains the first segmental structures in the state of New Mexico. The project is being built for the New Mexico State Highway Transportation Department and will add eight precast segmental ramps to the busy and vital I-25 and I-40 interchange in Albuquerque. The eight precast ramps are part of the 55 bridges included in the two-year schedule. The project, designed by URS Corporation, increases the designed traffic capacity of the interchange from the initial 40,000 vehicles per day design in 1965 to 400,000 vehicles per day. The project was awarded to Twin Mountain Construction II based on a bid of $270 million.

The eight precast segmental ramps consist of Ramp SE (15 spans, 767 m in length), Ramp NW (11 spans, 565 m in length), Ramp WS (6 spans, 288 m in length) Ramp SW (4 spans, 184 m in length) Ramp NE (4 spans, 199 m in length) Ramp ES (4 spans, 181 m in length) Ramp EN (4 spans, 198 m in length) and Ramp WN (4 spans, 190 m in length). All eight ramps are being erected in balanced-cantilever with a ground-based crane.

The geometry of the project consists of an assortment of horizontal and vertical curves that winds the ramps through the intersection with a minimum radius of 182.5 meters (Figure 21). The segmental ramps contain two different cross-sections, for a double-lane and for a single-lane ramp. The box sections are 2.790 meters deep and measure 12.914 m wide for the double-lane and 9.914 m wide for the single-lane ramps.

Due to the proximity of the precasting yard adjacent to the site, the segment lengths were adjusted for both the pier segments and typical segments to maximize the segment weight and reduce the number of segments. Typical segment lengths were increased from 3.0 meters to 4.0 meters for the double-lane segment and from 3.6 meters to 4.5 meters for the single-lane segments. The pier segments designed as split-pier segments were modified to be cast as a single unit. By increasing the segment lengths and weights the number of segments was reduced from 822 to 662 segments, eliminating 160 segments from the critical path of precasting. The construction engineering for the project, including the construction modifications, is being provided by Finley McNary Engineers. Precasting of the segments began at the beginning of June of 2000. Over 425 segments have been cast by January of 2001. The precasting is being performed in five casting beds, which were provided by Southern Forms.

The ramps are being erected using the balanced-cantilever method with a ground-based crane (Figure 22). Falsework towers on each side of the pier column are used to stabilize the cantilever during erection. The bearings were equipped with longitudinal stops for restraints during erection and provisions for adjusting the cantilever for geometry control. D.S. Brown is providing the bearings and expansion devices. Erection of precast segments began at the beginning of July of 2000 with Ramp SE. As of January of 2001, Ramp SE erection is completed and Ramp NW is under construction.

The project requires the Contractor to provide quality control and construction engineering inspection for the project. Post Buckley Schuh & Jernigan was hired by Twin Mountain Construction II to provide quality control for the project with Finley McNary Engineers providing the construction inspection services for the segmental work.